1. Field of the Invention
The present invention relates to a seek servo control method and device for a disk drive, and more particularly, to a seek servo control method and device for performing seek servo control according to a variation in a power supply voltage for the disk drive.
2. Description of the Related Art
In general, a disk drive, an example of a data storage apparatus, reads or writes data from or to a disk by using a magnetic head. As the disk drive has a tendency to have a high capacity, a high density, and a compact size, a bit per inch (BPI) in a rotational direction and a track per inch (TPI) in a radial direction of the disk drive become large. As a result, there is a demand for a highly accurate mechanism in the disk drive.
One of criteria for disk drive performance is a seek time. The seek time denotes a time taken to move a transducer from a current cylinder to a target cylinder when a disk drive writes or reads information.
A track seek is performed as follows. First, design position, velocity, and acceleration trajectories for a seek length are generated. Next, with reference to the design acceleration trajectory, errors between design position and velocity trajectories and real position and velocity trajectories are provided to a feedback process to generate a seek current. Finally, the generated seek current is applied to a voice coil motor (VCM) to move a transducer across tracks. These design trajectories are derived from their respective servo system models. For a variety of practical reasons, the servo system models are approximated to a simple ideal model. However, a real system is not equal to the simple ideal model due to various limitations. This is called a non-ideal problem. In order to avoid the non-ideal problem, there have been proposed several approaches for partially employing a non-ideal model into a real system and limiting performance of the real system.
A representative approach is a seek control technique disclosed in U.S. Pat. No. 6,801,384. The seek control technique is designed with supply voltage limitation to a sinusoidal seek servo algorithm which is disclosed in U.S. Patent Application Publication No. 2001/0050827.
In the seek control technique, a real supply voltage has a voltage tolerance of +/−10% of a standard supply voltage Vs. Therefore, the seek control system according to the voltage limitation should be designed in terms of 0.9 Vs of the most serious environment. As a result, there is a problem in that the seek performance deteriorates even in a standard voltage environment.